Process of producing chemical wood-pulp.



1., 0. LUNDBERGL, PROCESS OF PRODUCING CHEMICAL WOOD PULP.

APPLICATION FILED NOV- 9. I914- Patented Feb. 19,1918.

WWW 67W ingsii JACOB OTTO LUNDBERG, OF FLATEBY, NEAR LILLESTBOMMEN, NORWAY.

PROCESS OF PRODUCING CHEMICAL WOOD-PULP.

Specification of Letters Patent.

Application filed November 9, 1914. Serial No. 871,185.

To all whom it may concern:

Be it known that I, J AOOB O'rro LUND'BERG, a subject of the King of Sweden, residing at F lateby, near Lillestrommen, Norway, have invented certain new and useful I-mprovements in Processes of Producing Chemical Wood-Pulp; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying draw.-

mar ed thereon, which form a part of this specification. v

The present invention relates to the manufacture of chemical wood pulp according to the sulfate or soda method and consists in an improvement in the method of supplying the heat necessary for the digesting operation. As is known the usual method of supplying the heat is to introduce steam into the digester, when this-latter has been charged with wood and digesting liquor.

By this method however great quantities of water will be introduced into the digester so that the digesting liquor-is highly diluted during the digesting operation. For various reasons this is a very great disadvantage and it has therefore been proposed to effect the raising of the temperature by maintaining the digesting liquid alone or together with the wood or other material to be treated in circulation through a special heating apparatus outside of the boiler. This method is however also connected with various disadvantages. Thus the raising of the temperature takes a considerable time while on the other hand the circulation is rendered diflicult by the wood or other fibrous material under treatment.

According to the present invention the heating is effected in the manner that the quantity of liquor which at the beg1nn1ng of each digesting operation is introduced into the digesting boiler containing the and to letters or figures of reference in a system of vessels or pipes and the like) from which the hot liquor is blown into the Patented Feh. 19, 191s.

digester in the quantity necessary for each digesting operation. A small quantity of heat may 1n some instances also be supplied to the digester in a known manner. The

process may for instance be carried out inl the manner below described reference being hadto the accompanying diagrammatic drawing which illustratesa plant for carrylng out the process.

In the drawing 1 designates a reservoir for fresh digesting liquor. 2 is a reservoir for black liquor (that is liquor which has already been used), 3 and 4: designate the digesters.

510 designate connection pipes between the reservoirs and the digesters.

11 and 12 are steam pipes for efl'ecting the heatin of the liquor 1n the reservoirs. Instead o arranging steam pipes inside of the reservoirs other indirect heating methods may of course be employed. The fresh liquor is heated .inlthe reservoir 1 .to a comparatively high temperature for intures for instance down to 140 C. may however also be employed without departing from the idea of this invention. In the following description it is assumed that the digester 3 contains a charge, which has just been finished. while the digester 4 is empty.

wood or other fibrous material to be treated a spherical, cylindrical or tubular shape or The valves in the pipes 10 and7 are now opened and the black liquor from the digester 3 in which a pressure of about 8 kg.

per cm may be assumed to prevail, is blown into the black lye reservoir 2 whereupon the digester is emptied in the usual manner. It may now be assumed that the black liquor in the reservoir 2 is brought under a ressure of about 5 kg. per cm he charging of the di ester 4 is now efe fected b rst filling t e digester with wood, w 'ereupon a part of the black liquor in the reservoir 2 is blown into the digester.

The digester is then filled with highly heated fresh liquor which is blown into the digester from the reservoir 1. The digesting operation then continues while supplymg some heat in the usual manner. vThe emptying and charging of the digester is then continued in the manner above described? The process is preferably carried out in such manner that the temperature falls from the beginning. of the dlg'esting. operation.

stance 180 C. Higher or lower temperaof a much better quality,than that obtained until it is finished, but it may also in some cases be oi advantage to maintain the temperature constant during the whole digesting operation or to cause a small rise in temperature at a certain stage of the operation. v

Before the reservoir 2 is charged with fresh liquor to be heated it is of'advantage to empty the same completely and to do away with the pressure in the same by blowing ofl' steam; Hereby the use of high pressure pumps for filling the reservoirs is avoided.

By working according to the present invention which may of course be modified in various manners, very important advantages are obtained over the usual methods. Thus it has been found, that the formation of malodorous substances (mercaptanes and the like) which takes place in connection with the usual method of boiling, is quite insignificant when the process is carried out in accordance with the present invention. Moreover the plantand apparatus necessary for carrying the invention into efl'ect is very simple for instance as regards pipeconduits, valves. and the like. The consum tion of steam is uniform and continuous, which as will be understood is of the greatest advantage. Further the black liquor obtained is according to the usual methods, so that the recovering of soda from the same becomes more rational. Another advantage consists therein that a white liquor (freshly prepared liquor) of a lower concentration can be employed because the liquor is not diluted during the digesting operation as is the case when the-quantity of heat necessary is supplied by means of steam directly introduced into the digester.

As is well known it is usual in the soda cellulose factories to preheat the liquor to some extent before it is supplied to the digesters but the heat which has been supplied in this manner has been much too small to reduce to any considerable degree the quantity of heat to be supplied to the digester during the digesting operation.

I claim:

1. The process of digesting wood pulp by the sulphate or soda process, whichcomprises filling a digester-with the wood to be treated, storing the digesting liquor in a separate container, indirectly steam-heating the liquor therein under pressure without circulation or the same by passing steam under high pressure in a conduit through naeaaeo the container out of contact with the liquid so as to produce a temperature suficiently high that the amount of heat necessary for the digesting process is stored in the liquor, supplying the liquor so heated to the digester in a quantity sufficient to simultaneously edect the digesting and supply the necessary heat, and completing the digestion without circulating the liquor through the,

digester.

2. The process of digesting wood pulp by the sulfate or soda rocess which comprises, filling a digester with the wood to -be treated, storing the digesting liquor in a separate container, heating a quantity of black liquor in a separate container, supplying the heated liquor under pressure to the digester, heating freshly prepared digesting solution in a separate container to a high tempera? ture without circulation of the same by passing steam under high pressure through the solution out of contact therewith so as tocproduce so high a temperature that the heat necessary for essentially the whole digesting process is stored in the solution, supplying a quantity of the solution so heated to the digester, and completing the di-' gestion without circulating the liquid contents ot' the digester.

3. The process of digesting wood pulp by the sulfate or soda process which comprises filling a digester with wood to be treated, drawing oil the black liquor from a digester into a separate contamer, reheating the liquor in the latter by assmg steam under pressure through said 1quor out of contact therewith, supplying a portion of the heated liquor to the digester containing the wood,

heating a freshly prepared digesting solu- JACOB OTTO LUNDBERG.

Witnesses:

E, un'ronmsmr, Trees, 1. 

